1. Technical Field
The present invention relates to a detection circuit, a sensor device, and an electronic instrument.
2. Related Art
A known conventional infrared detection circuit uses a pyroelectric element. A human body emits infrared radiation at wavelengths in a vicinity of 10 μm, and the conventional infrared detection circuit can detect the existence of a person or acquire temperature information regarding a person in a non-contact fashion by detecting such radiation. Thus, this kind of infrared detection circuit can be used to detect intruders and to measure physical quantities.
Examples of known technologies for infrared detecting circuits are disclosed in Japanese Laid-Open Patent Publication No. 59-142427 and Japanese Laid-Open Patent Publication No. 6-265411. The conventional technology presented in Japanese Laid-Open Patent Publication No. 59-142427 is configured to read a pyroelectric current of a pyroelectric element while using a chopper to cyclically expose and interrupt exposure of a pyroelectric element to infrared radiation.
The conventional technology presented in Japanese Laid-Open Patent Publication No. 6-265411 uses a method in which a pulsed voltage is applied to a pyroelectric element. That is, an amount of spontaneous polarization exhibited by the pyroelectric element, which is made of a ferroelectric material, changes in response to a temperature of the pyroelectric element and the temperature of the pyroelectric element changes due to infrared radiation incident on the pyroelectric element. Thus, by measuring an amount of surface charge of the pyroelectric element, which changes in response to the amount of spontaneous polarization, an amount of incident infrared radiation can be measured.